Time for an inspection
The Directive requires these systems to be inspected by a competent and accredited person who belongs to a scheme approved by the Department for Communities and Local Government (CLG). There are several such schemes, one of which is operated by CIBSE Certification. This is a scheme for air conditioning assessors for both complex and simple systems, and is one of a range of accreditations offered by CIBSE Certification in support of the Energy Performance in Buildings Regulations. CIBSE also accredits inspectors to undertake these inspections in Scotland and Northern Ireland.
Where a building has more than one system, they all require inspection. If they are controlled by the same person (or organisation) then the capacity of the systems should be aggregated to determine the overall size and, therefore, when the first inspection is required. The Regulations define a ‘responsible person’ who is required to commission the inspection and to receive and retain a report.
These inspections are intended to give owners and operators information about the performance of their buildings and plant, enabling them to identify opportunities to save energy and cut operating costs. Whilst the inspection is mandatory, nobody currently has to act on any advice given, although in the current economic climate, ideas that help to cut both energy consumption and costs must surely be welcome.
The procedure is kept simple, and aims to identify poor performers and minimise costs and disturbance. CIBSE, in partnership with the HVCA, BSRIA, Institute of Refrigeration and others has produced a detailed inspection procedure in CIBSE TM44. This describes what should be done when inspecting plant, and gives advice on how to assess cooling loads in the building, to enable the assessor to meet the requirement to advise on the size of the system in relation to the cooling load. The following actions should be taken by an accredited assessor.
Inspection of documents and records
The first step in the inspection is to review records of the air conditioning system. In more recent buildings this should be found in the building log-book, which is now a requirement under the Building Regulations, otherwise system descriptions and commissioning records may be needed to find plant types, sizes and locations.
This information may provide useful performance factors such as the Specific Fan Power of air distribution systems, while records of energy consumed or hours run may indicate excessive use and potential control issues. Where data is not provided the assessor may use rules of thumb to estimate cooling load, current levels of occupancy, activities being carried out, heat generating equipment, solar and other heat gains.
Inspection of equipment
Reviewing maintenance records and examining equipment allows comparison with industry good practice, and confirms that the plant matches the records, which should be updated if required. Where this shows the system is already well maintained and controlled, then aspects of the wider physical inspection may be omitted. However, where maintenance has not been undertaken, or information is missing, the inspector may need to investigate further.
Advice for system improvements
The assessor shall highlight any faults with the equipment. The size of the system is compared to the load to check that the system is of an appropriate size. The assessor can also suggest where there are opportunities to reduce the cooling load or to use more efficient equipment such as variable speed fans with relatively short payback times, or the manager may be informed of the availability of higher efficiency cooling plant to consider when systems are renewed.
The air conditioning inspection report
The report should ideally be kept as part of the building log-book, so it is readily available to review or act on its advice, prepare an Energy Performance Certificate or carry out the next five yearly inspection.
The regulations apply to air conditioning systems for comfort cooling, in the same way as Part L of the Building Regulations, and the corresponding documents in Scotland and Northern Ireland. Systems which are installed to condition environments for equipment or processes are currently not within the scope of the inspection requirement. In practice these systems are often specialised and business critical and so they are closely monitored. While the general principles of inspection will apply to such installations, different knowledge and skills may be needed to understand their design and control, and to assess their sizing and opportunities for improvement.
Air conditioning inspections are now a part of the responsibility of the building manager, but with the guidance from CIBSE they need not be a burden.
Efficient Air helped the CLG (The Department of Communities and Local Government) to improve the energy performance of its Eland House HQ by 12.6%, which equates to energy saving of 662,055 kWh valued at £40,909. The Carbon Dioxide reduction is calculated at 250 tonnes.
As the department responsible for implementing the European Performance of Building Directive (EPBD) CLG were keen to ensure they were amongst the first to get EPCs and DECs and to commission an air conditioning inspection on their headquarters building – Eland House, Bressenden Place in London.
The inspection was carried out by leading HVAC energy saving specialists Efficient Air under the supervision of the company’s head of consulting, Darren Jones – the UK’s first CIBSE Low Carbon Energy Assessor for complex AC systems.
The Air Conditioning inspection was the third step in assessing the energy performance of the 11 story glass and steel framed office block, it had already received an ‘F’ rating on its DEC, compared with a ‘C’ rating on its EPC.
Efficient Air’s air-conditioning inspection report included an action plan – the energy saving opportunities detailed in this plan alone would improve the current operational efficiency of the building as shown on the DEC from an ‘F’ to an ‘E’ rating.
The 10 point action plan
- Standardise on temperature set-points to eliminate fighting between units and chilled beams
- Ensure a dead band of at least 3°C (+/-1.5°C) is factored into BMS strategies to prevent simultaneous heating and cooling between the Air Handling Units, perimeter heating circuits and the chilled beam units
- More frequent temperature and pressure sensor calibration
- Replace faulty cooling and heating valves
- Reduce the over supply of airflow on Air Handling Unit 4
- Set control damper actuators for free cooling and heat reclaim optimisation from re-circulated air
- Increasing the frequency of filter changes
- Replace old technology fans with new high efficiency technologies
- Change the control of the ‘on floor chilled’ water pump to reduce the use of the chilled beams during winter
- Repair and improve lagging on ductwork and pipe-work to minimise losses